Department of Pediatrics, Washington University School of Medicine, Saint Louis, USA.
BMC Evol Biol. 2011 Jun 27;11:183. doi: 10.1186/1471-2148-11-183.
Escherichia coli is one of the best studied organisms in all of biology, but its phylogenetic structure has been difficult to resolve with current data and analytical techniques. We analyzed single nucleotide polymorphisms in chromosomes of representative strains to reconstruct the topology of its emergence.
The phylogeny of E. coli varies according to the segment of chromosome analyzed. Recombination between extant E. coli groups is largely limited to only three intergroup pairings.
Segment-dependent phylogenies most likely are legacies of a complex recombination history. However, E. coli are now in an epoch in which they no longer broadly share DNA. Using the definition of species as organisms that freely exchange genetic material, this recombinational dormancy could reflect either the end of E. coli as a species, or herald the coalescence of E. coli groups into new species.
大肠杆菌是所有生物学中研究得最透彻的生物之一，但目前的数据和分析技术很难确定其系统发育结构。我们分析了代表菌株的染色体中的单核苷酸多态性，以重建其出现的拓扑结构。
大肠杆菌的系统发育因所分析的染色体片段而异。现存大肠杆菌群体之间的重组主要仅限于仅三种群体间配对。
片段依赖性系统发育很可能是复杂重组历史的遗留物。然而，大肠杆菌现在正处于一个不再广泛共享 DNA 的时代。根据物种的定义，即可以自由交换遗传物质的生物体，这种重组休眠可能反映了大肠杆菌作为一个物种的终结，或者预示着大肠杆菌群体融合成新的物种。
